A hydraulic valve is already known from DE 198 08 279 A1. The valve includes a plastic housing. The plastic housing is injection molded about a magnetically conductive insert bushing. A pole core with a pole core cone is inserted into the combination including the plastic housing and the insert bushing. A plastic component that is designated as a base is inserted into the insert bushing, wherein the plastic component is injection molded about a pot base of a pot shaped pole tube. A disc shaped pole flange is placed onto the pole tube in the area of the pot base. In the pole tube, an anchor is arranged movable in axial direction. A piston is inserted into the anchor, wherein the piston is supported in a hydraulic bushing which is configured in one piece with the pole core.
From DE 10 2009 042 888 A1, a proportional valve is already known whose pole core cone, designated as control cone, has a trumpet shape. The pole tube designated as steel sleeve includes a separation layer which can be a low friction lacquer, PTFE or a nickel-PTFE coating.